1. Field of the Invention
This invention generally relates to a device for developing an electrostatic latent image formed on an image bearing member by application of a thin film of toner particles charged to a predetermined polarity, and, in particular, to a developing device for developing an electrostatic latent image using a single component developer, in particular, a non-magnetic single component developer.
2. Description of the Prior Art
A developing device is commonly used for developing an electrostatic latent image formed on an image bearing member, such as a photosensitive member, in electrophotographic or electrostatic recording system. One type of such a developing device uses a two-component developer comprised of toner and carrier beads and there is another type which uses a one-component developer having no carrier beads. In the former type, development can be carried out relatively stably and a developed image of excellent quality can be obtained; however, the mixture ratio between toner and carrier beads must be maintained properly so that there must be provided a mechanism therefor which tends to complicate the structure of imaging systems.
It is thus desirous to use a developing device employing a one-component developer. Such a one-component developer is typically comprised of a mixture of toner and a magnetic material which serves as the carrier beads in the two-component developing system. In a developing device using such a one-component developer containing a mixture of toner and a magnetic material, typically, a developing sleeve is rotatably provided with a magnet roll disposed therein so that the one-component developer is magnetically attracted to the peripheral surface of the developer sleeve. And, a thin film of one-component developer formed on the developing sleeve and charged to a predetermined polarity is applied to an electrostatic latent image for development thereof.
In this manner, in a prior art developing device using a one-component developer, the developer itself is made to be magnetically attractable and thus it is carried on the developing sleeve as magnetically attracted thereto and then it is electrically transferred to the image bearing member having an electrostatic latent image selectively from the developing sleeve. Thus, the so-called one-component developer is required to contain therein a magnetic material in addition to a coloring material, such as carbon black, and, thus, the manufacture of a developer is rather limited as far as selection of material is concerned. It is thus desired to provide a developing device which is capable of using a non-magnetic one-component developer.